我在继兄弟的生日那天给了我的屁股！

I woke up in the morning and noticed that my stepbrother was sad and sitting at home. It was his birthday. He was playing a game console and didn't pay much attention to me. I decided to please him and jokingly offered to fuck me in the ass. I was very surprised when he agreed! My parents were not at home and I had to fulfill my promise.